With voiceover
Videos provide an enormous advantage when you deliver your message to potential customers: you can involve more sensory and cognitive inputs by offering visuals, sound and voice. People use their ears to augment what they see. When we see events that are "mute", we subconsciously think that something is wrong. We are less trusting and prepare ourselves for danger. In terms of evolutionary psychology, think of our ancestors who survived by hearing their enemies coming in the distance. After thousands of years of living in society, people are really good at picking up on the subtle nuances and intonation of how others speak! We use this information to form impressions of the people we talk with. So when we hear information given in a pleasant, confident voice, we begin to subconsciously trust the speaker. Voice, timbre and tone are an important way of influencing viewers. Voice is also the simplest way of conveying emotion and setting the tone of a video. [rollup="Example. Darklings II Teaser"]Without voiceover
If your video's main message can be expressed visually (as can be done for some simple and obvious products), voiceovers may not be needed at all. For products like these, it's hard to write a good voiceover text because there is almost nothing to say. [rollup="Example. Two teasers"]
Localizing a video without voiceovers is easy! Just change the labels shown on screen.